Regardless of the precise nature or function of an apparatus in which components are subjected to wear by a material flow, wear causes need for repair and replacement of components and delays in use of the apparatus while one or more worn components are identified, inspected, removed, and replaced. Wear of components adds to the expense of maintaining and operating the apparatus.
As a result of persistent wear caused by material flows, components on construction equipment exposed to material flow must be replaced. Replacement of components causes “down time” to repair, refit, and replace components. Additional expenses are associated with replacing the worn part or component, inventorying replacement components, and delivering a replacement component to what is often a remote site.
For example, a wide variety of impact rock crushers are used in commerce to reduce the size of larger earth materials to smaller sized aggregate. The construction industry trades employ a variety of impact crushers to reduce large aggregate to aggregate sizes and shapes required to satisfy construction specifications for mixtures and admixtures of aggregate with cement and other ingredients and for further processing of size reductions, chemical leaching, and other stages of use. The construction industry's use of impact crushers is but one example of the need to reduce wear caused by a materials flow in an apparatus used to effect the size of aggregate in the materials flow, to make substantially uniform the size of aggregate in a materials flow, and to prepare materials for further processing.
Generally, impact rock crushers provide a device for introducing aggregate into a device for crushing the aggregate. Many impact crushers are designed to rely on centrifugal force to disperse large aggregates through the crusher and to impact the aggregate against a wide variety of impact crusher components to break up, reduce in size, and ultimately eject from the crusher, aggregates composed of desired shapes, sizes, and consistency.
Impeller impact rock crushers may include but are not limited to one impeller table, having a central feed body and impeller shoes attached to an impeller assembly. The shoes, in combination with centrifugal force, hurl and direct an aggregate flow generated by operation of an impeller assembly against one or more anvils located within the crusher. Both the central feed body and impeller shoes on the impact impellers are subjected to substantial wear caused by material flow.
The front face of prior art impeller shoes are radially oriented with respect to the central axis of the impact impellers. The impeller shoes change the velocity of the material flowing outwardly along the impeller table due to centrifugal force. The accelerating mass of the material applies a substantial force vector normal to the surface of the shoe. The normal force against the surface of the shoe results in high friction and high wear rates of the shoe.
Efforts have been devoted to improvements in the design and construction of components of impact crushers to reduce the cost of acquiring and operating crushers, to enhance wear resistance of the component parts of crushers, and to facilitate rapid replacement of worn parts of crushers to enable the user of crushers to lose the least possible amount of time during which a crusher is inoperative due to worn parts.
Such improvements are exemplified by U.S. Pat. No. 5,954,282 issued Sep. 19, 1999. The Britzke et al. patent is instructive on describing how components in an impact crusher are exposed to wear during operation of an impact crusher. All components of an impact crusher exposed to a material flow of aggregate, as exemplified in Britzke et al. U.S. Pat. No. 5,954,282 and other impact crushers, are subject to abrasion, decomposition, fracture, friction, impact, pulsation, wave action, grinding, and other actions causing wear to components of an impact crusher this is due to the velocity, acceleration and composition of aggregate flows against, across, and around the components during operation of a crusher (collectively, “wear”).
U.S. Pat. No. 5,954,282 to Britzke et al. discloses an impeller assembly including wear resistant rods press fit into bores formed in the vertical crusher assembly. Vertical impact crushers such as U.S. Pat. No. 5,954,282 incorporate a flat central feed disc for receiving material from a hopper. The Briztke et al. '282 U.S. patent employs hard material rods that are interference press fit into bores milled into a ferrous body. The hard material used to construct the rods in the Britzke et al. '282 patent has a much greater wear resistance than the ferrous material used to construct the body.
Prior art impact crushers constructed according to the Britzke et al. '282 disclosure have suffered from drawbacks during operation in the field. The hard material rods in Britzke et al. '282 themselves have proven durable in resisting wear but the ferrous material of the body at 12 in Britzke et al. '282 wears out at a predictably accelerated rate in comparison to the rods. As the exposed surface of the ferrous body that fixes and holds the rods recedes the depth of the bores at 24 in Britzke et al. '282 shorten exposing more of the rod. As the body ferrous material recedes, the interference press fit between the ferrous body and rods shorten and weaken until eventually on account of the weakened joint the rods are then easily knocked out by aggregate. In such impeller plates and impeller shoe designs as described in Britzke et al. '282, the press fit compact wear rods on the impeller shoes and center feed disc prematurely become dislodged by aggregate material. In efforts to protect hard material rods from wash out, prior designs have attempted to position adjacent hard material rods closer together, but have been unsuccessful. In these prior designs it was necessary that the spacing between the rods became so small that the strength and integrity of the ferrous body for receiving and holding (interference fit) the insert rods weakened and softened to the point that the interference fit was insufficiently strong to hold the rods in place.
The “washed out” compact rods are slung against the anvil and other components of the crusher by the centrifugal force generated by the rotating impeller. The hard material rods cause damage to the components of the impeller that are often made of softer materials. These compact rods that broke free of the impeller or shoes were hurled against the anvils and other components of the vertical shaft impeller (VSI) causing accelerated wear and greater damage to the VSI as the compact inserts bounce back and are constantly flung within the impeller against anvils and other components. On occasion such compact inserts would knock loose other compact inserts resulting in more destruction and even greater acceleration of damage within the VSI.
It is an object of the present invention to reduce the frequency of impeller shoe and central feed body maintenance required in the operation of impeller rock crushers. It is believed that the present invention results in saving of expenses resulting from less maintenance labor, cost of replacement components and less down time.
What is needed, therefore, is a cost effective device for reducing the wear rate of components of apparatus subjected to operational wear. Particularly, what is needed is a device for reducing wear of components of an impact aggregate crusher caused by a material flow of aggregate during operation.